I agree with Rusty and Dugaboy, get a 450/400.
When I was shopping for my first double I wanted a 450 so I could shoot 350 gr. Hornady .458 bullets for deer and pigs as [practice before going to Africa. I test fired a 450 No2 and a 450/400 3 1/4" Nitro on the same day. I liked them so well I bought them both. I felt my wife could use the 400 when she went to Africa and it could serve as a spare to the 450 for me.
My 450 No2 is my most favorite rifle ever. However, If I had bought the 450/400 first I just might have 2 of them. My 450 No2 has 28" bbls and weighs 11 3/4 lbe. It handles like a fine shotgun but is a little heavy for an allround double suitable for North America/Africa.
My 450/400 weighs 9 1/4 lbs and also handles like a fine shotgun. While I have hunted with the 450 in TX and Africa, I have used the 450/400 in Montana, Alaska, as well as TX. It has taken deer several pigs 2 caribou and black bear.
For the sport hunter is has plenty of power and penetration for any African Game and would make an excellent brown bear rifle.
My first recomendation would be to find a British Double.
As you know Searcy will make you a 450/400 also tell him you want it to weigh not over 9 1/2 lbs with 26 inch bbls. They do kick quite a bit less than a 470.
I have a load with 300 grain Hawk bullets that is DYNO-MITE

on deer and pigs. For everything else I have used 400 grain Woodleighs.
For the "modern" sport hunter I consider the 450/400 the best choice for your first double. Also as your "last" double for the same reasons, they weigh less and kick less.
You will never regret buying a 450/400.